Emissions Model Planning and Design Review Mobile Sources Emissions

1
Emissions Model Planning and Design
ReviewMobile Sources Emissions

• Presented by
• Alison K. Pollack
• ENVIRON International Corporation
• Denver, CO
• 9 January 2004

2
Motor Vehicle Model Scope

• Spatial resolution link-level and county-level
  inputs and emissions
• Temporal resolution able to handle hourly
  inputs, generate hour-specific emissions
• Vehicle classes (8 or 28?)
• Emission modes (keep evaporative, running
  exhaust, start exhaust separate for speciation
  and allocation)

3
County Data Inputs County-level vs. Gridded
Temperatures/Humidity

• Gridded Temp/Hum - Pros
• Improved accuracy
• (esp. VOC, CO)
• Direct use of available meteorological data

• Gridded Temp/Hum - Cons
• Increased number of scenarios for MOBILE6 runs ?
  increased emission factors table size, MOBILE6
  execution time
• Requires VMT data to be gridded first
• HPMS VMT data records will increase ? longer
  execution time for emission calculations

4
MOBILE6 Execution Descriptive Output vs.
Database Output

• Database Output - Pros
• Can obtain hour-specific emission factors
  (i.e., capture correct hourly soak
  and diurnal distributions, factors affecting A/C
  use such as solar flux)
• Format directly importable to data table

• Database Output - Cons
• Much larger output file sizes
• But, the number of records in
• the output can be reduced by combining across
  model years, vehicle classes, emission mode, and
  road types.
• MOBILE6 code modifications required

5
MOBILE6 Execution Handling of Hourly Starts
(Trips) Data

• Start emission factors (g/mi) are obtained from
  the database output along with default hourly VMT
  and starts per vehicle assumed by the model.
  These can be combined to obtain g/start emission
  factors.
• The hourly soak distribution (which can be
  modified in MOBILE6 input) is included in the
  emission factor.

6
MOBILE6 Execution Determination of MOBILE6
Scenarios

• Each scenario is a unique combination of road
  type, speed, temperature, and humidity.
• Binning approach
• Bin speeds, temperatures, and humidity to reduce
  the number of scenarios. Model all possible
  combinations of the 3 types of bins (and 4 road
  types).
• Some unneeded scenarios (i.e., combinations of
  road type, speed, temperature, and humidity not
  in the input data) will be run.
• Single temperature used in each scenario, thus
  zeroing the diurnal emission. Separate set of
  runs required to obtain diurnal emission factors.

7
MOBILE6 Execution Determination of MOBILE6
Scenarios (concluded)

• Smart selection approach
• Run scenarios for actual hourly temperatures and
  relative humidity with speed bins for each road
  type for each county/grid cell.
• Could further reduce scenarios by binning
  temperature and relative humidity (and selecting
  only bins needed)
• Database output hour-specific emission factors
  capture the correct speed, temperature, humidity,
  road type/cycle, and other time of day-dependent
  factors.
• Diurnal emission factors are directly useable
  (i.e., nonzero)

8
MOBILE6 Execution Data Handling/Functionality

• Should commands requiring additional information
  be handled as text strings?

• Text strings - Pros
• Fewer elements in parameters table.
• Easier preparation of inputs imported into the
  parameters table.

• Text strings - Cons
• Less precise control over individual sub-elements
  of the command line information

• Should MOBILE6 commands for turning off Federal
  controls (e.g., NLEV, Tier 2, HDDV 2007) be
  deactivated?

9
Status of Design Process

• Draft design document awaiting resolution of
  above issues before completion.
• ENVIRON discussing with EPA modifications to
  MOBILE6 code.
• ENVIRON requests TDM output formats from LADCO
  for development of data input conversion tool
  (format to RPO Data Exchange Protocol).

10
NONROAD Modeling Scope

• Spatial resolution county-level unless
  consistent set of inputs for smaller area are
  provided
• Temporal resolution daily hourly estimates
  derived from daily
• Emissions by equipment type (SCC)
• Emission modes (keep evaporative and exhaust
  separate for speciation and allocation)

11
Source Categories not in NONROAD Commercial
Marine, Aircraft, and Locomotive

• Treat as area sources
• Emissions emission factor activity indicator
  by SCC
• Emission factors from AP-42
• Alternative methods available for possible later
  incorporation (e.g., EDMS for aircraft)

12
NONROAD Execution Deriving Hourly Emission
Estimates

• Two possible approaches
• Apply 24-hour distributions to daily estimates
  based on SCC
• Develop hourly inputs and run NONROAD for each
  hour.
• Input-intensive need hourly activity inputs by
  SCC
• Computationally intensive
• Need to post-process to get correct diurnal
  emissions

13
NONROAD Model Enhancement Add NH3 Emissions
Estimates

• Develop technical approach in consultation with
  OTAQ
• Modifications to NONROAD core model, Reporting
  Utility, and Graphical User Interface required to
  run this outside OPEM
• Schedule depends on availability of other NONROAD
  updates expected
• Revised growth and scrappage algorithms
• Incorporation of Sept 2002 Large SI evaporative
  standards
• New release expected in spring with final nonroad
  diesel Tier 4 standards